Figure 3. Fluorescence turn-on probe for the detection of Hg²⁺.

(a) Normalized emission spectra of TPE-S (20 μM) in the presence of various metal ions ([Hg²⁺], 3 × 10⁻⁴ M; other ions, 6 × 10⁻⁴ M) excited at 361 nm in CH₃CN-H₂O mixtures with the water fraction of 98%. (b) Fluorescence responses of TPE-S (20 μM) to various metal ions ([Hg²⁺], 3 × 10⁻⁴ M; other ions, 6 × 10⁻⁴ M) excited at 361 nm in CH₃CN-H₂O mixtures with the water fraction of 98%. Inset: The corresponding fluorescence photos of TPE-S reacted with various metal ions. (A) TPE-S; (B) TPE-S+Hg²⁺; (C-T), Ag⁺, Fe³⁺, Cu²⁺, Pb²⁺, Co²⁺, Cr³⁺, Al³⁺, Cd²⁺, Mg²⁺, Mn²⁺, Ba²⁺, Fe²⁺, Ca²⁺, Ni²⁺, Zn²⁺, Li⁺, K⁺, Na⁺.